This invention relates generally to recovery of heat from hot gas streams, and more particularly to improvements in heat recovery apparatus whereby efficiency of power production is enhanced.
Systems to generate power from heat in the exhaust of heavy frame gas turbines have been used extensively. The heat is typically used to boil water at one or two pressures and superheat the steam flows. The resulting steam is used to power a steam turbine.
However, application of this conventional technology to aero derivative gas turbines and reciprocating engines, which have lower exhaust gas temperature and flow than heavy frame gas turbines, has been very limited. The reason is that the requirement to boil steam at a constant temperature results in a so called xe2x80x9cpinch pointxe2x80x9d limitation which reduces the thermodynamic efficiency and reduces the amount of exhaust heat which can be utilized for power generation. Application of organic working fluid systems is precluded because the exhaust gas temperature are too high for fluid stability and reasonable conversion efficiency. There is need for means to efficiently utilize this source of wasted energy.
It is a major object of the invention to provide improved apparatus and methods to meet the above need.
Basically, apparatus embodying the invention comprises:
a) a chamber having inlet and outlet porting for flow through of hot exhaust gas, in the chamber interior,
b) separate heat exchanger structures in the chamber interior, to receive heat transferred from the exhaust gas, the structures receiving pressurized liquid for flow in different paths through the ducts, to develop different pressures and temperatures without use of boiler drums,
c) the arrangement and sizing of the structures being such that they contain and like pressure or pressures of fluid, the fluid caused to flow in side-by-side relation with structures containing different pressures and generally counter-current to the exhaust gas flow,
d) the structures configured such that adjacent structures intercept different fractions of the gas stream,
e) the structures having outlets to communicate with a fluid driven turbine or turbines at different fluid pressure recovery zones.
It is another object to provide said streams from the structures to successively lower pressure zones of the turbine or turbines.
A further object is to provide the structures to extend substantially in parallel in the heat exchanger chamber, and to have different dimensions.
Yet another object is to provide a source of such hot gas, such as an internal combustion engine exhaust stream, in communication with heat exchanger inlet porting, for flow over segments of the structures in sequence, as for example tubing coils. Four such segments of structures of different lengths, may be provided.